Danny Sullivan covered the comScore search market share stats very well. Go read it. In short for the month of September:

Google: 66.1% (up 0.7 from 65.4%)Yahoo: 16.7% (down 0.7 from 17.4%Bing: 11.2% (up 0.1 from 11.1%)Ask: 3.7% (up 0.1 from 3.8%)AOL: 2.3% (no change)

Yahoo claims the boost is due to how Google Instant is counted. Yahoo said, “With products like Google Instant in the market, it’s more important than ever to understand how third-parties measure search queries and be judicious in how we use their numbers.”

I do like Tedster’s comments at WebmasterWorld:

In any event, I find this all funny. Being that Google cried foul when companies measured Yahoo Image Searches slideshow feature.

Forum discussion at WebmasterWorld.